Hostis dolum parat.

Yes, hostis can be either nominative singular or genitive singular in its dictionary form: hostis, hostis.

In this sentence, though, it is nominative singular, because it is the one doing the action of parat. In other words, hostis is the subject: the enemy prepares...

If it were genitive, we would expect it to depend on another noun, giving a meaning like of the enemy. Nothing in this sentence calls for that.

It is singular.

One clear clue is the verb parat, which is third-person singular: he/she/it prepares. So the subject must also be singular.

The nominative plural of hostis would be hostes: enemies.

Dolum is accusative singular.

That tells you it is the direct object of the verb parat. It is the thing being prepared.

The basic noun is dolus, -i, a second-declension masculine noun meaning trick, deceit, plot, or fraud.

Parat comes from paro, parare, meaning to prepare.

Here parat is:

• present tense
• active voice
• indicative mood
• third person singular

So it means he/she/it prepares or is preparing.

Because hostis is singular, the verb is singular too.

Latin usually does not use articles.

So:

• hostis can mean the enemy or an enemy
• dolum can mean a trick, the trick, a plot, or the plot

English has to choose an article, but Latin often leaves that to context.

Because Latin word order is much more flexible than English word order.

A very common neutral order in Latin is:

subject + object + verb

So Hostis dolum parat is a very normal arrangement.

Latin can do this because the endings show each word's role:

• hostis = subject
• dolum = object
• parat = verb

Yes, often they could.

For example:

• Hostis dolum parat
• Dolum hostis parat
• Parat hostis dolum

All of these can basically mean The enemy prepares a trick/plot.

The main difference is usually emphasis, not basic meaning:

• Hostis dolum parat = neutral order
• Dolum hostis parat = emphasis on dolum
• Parat hostis dolum = emphasis on the action parat

In classical Latin, hostis often means a public enemy, especially an enemy in war or an enemy of the state.

That is slightly different from inimicus, which more often means a personal enemy.

In many sentences, though, the simplest translation is just enemy.

It is a very natural Latin expression.

Literally, it means to prepare a trick or to prepare deceit. In smoother English, depending on context, it can mean things like:

• to hatch a plot
• to scheme
• to set a trap
• to plan a deception

So it is more idiomatic than a word-for-word English translation might suggest.

They are:

• hostis, hostis = enemy
• dolus, -i = trick, deceit, plot
• paro, parare, paravi, paratus = prepare

These are the forms you would usually look up in a dictionary or vocabulary list.